1. Field of the Invention
The present invention relates to an imaging unit and an image forming apparatus using the same, and more particularly, to an electrophotographic imaging unit for use in an image forming apparatus, such as a photocopier, facsimile, and printer, and an image forming apparatus using the same imaging unit.
2. Discussion of the Background
Electrophotographic image forming systems, such as photocopiers, facsimiles, printers, etc., employ an imaging unit in which various imaging components are assembled into a single unit. A typical architecture for electrophotographic imaging includes a photoconductor section accommodating a drum-shaped photoconductor and a developer section accommodating developer and a developer applicator or roller. When assembled, the photoconductor and the developer roller have a spacing or gap therebetween, where the developer passes from one surface to another to develop an electrostatic latent image on the photoconductor into visible form during operation.
As variations in the development process greatly affect print quality of the image forming system, maintaining a consistent gap between the photoconductor surface and the developer roller surface is important.
It has been a common practice to form a photoconductor drum axis or a developer roller axis movable within the accommodating section, and to adjust the movable axis relative to the other axis to obtain a desired gap between the photoconductor and the developer roller in the assembled unit. Such gap adjustment is awkward and inefficient in terms of productivity, requiring a special tool to bring the movable axis into proper position. Further, the conventional design involves complicated assembly and disassembly of imaging components, making it difficult to manufacture and maintain the imaging unit.
To overcome such drawbacks, a hinged dual-housing imaging unit has been proposed wherein a photoconductor housing and a developer housing are connected along a common axis around which both housings are pivotable. The photoconductor housing and the developer housing rotatably hold a photoconductor drum and a developer roller, respectively, with a spacing therebetween adjustable by pivoting the housings on the common axis. Both housings have surfaces to contact or mate with each other when the imaging unit is assembled, which restrict movement or pivoting of the housings to maintain the adjusted spacing between the photoconductor drum and the developer roller. The hinged housings can be opened away from each other to facilitate assembly and disassembly of imaging components for maintenance, and the imaging unit can be restored to its proper operational position merely by contacting or mating the corresponding surfaces of the hinged housings, without any precision positioning equipment required.
Despite its advantages over the conventional design, the above-described method based on hinged housings has a drawback in that consistency of the spacing between the photoconductor drum and the developer roller cannot be ensured because it is affected by various factors such as vertical and/or horizontal misalignment between the photoconductor and the developer roller, distortion of the accommodating housings, mismatching between the contacting or mating surfaces, etc., and is therefore hard to control. Addressing this drawback by requiring tight dimensional and positional tolerances is impractical due to high costs required to manufacture various such imaging components with high precision.
Moreover, the above method has another drawback in that the drum-to-roller spacing, once determined, is hard to modify, since it requires modification on the contacting surface that is integral with the photoconductor or developer housing.